In this paper, we use nonlinear optics and Runge-Kutta method to simulate and analyze the process of generating terahertz radiation by the optical rectification effect in zinc telluride crystals by mode-locked pulse (MLP) and noise-like pulse (NLP). For theoretical analysis, the second-order nonlinear effect is considered. Further, the slowly varying envelope approximation is assumed to be valid. Comparing the terahertz spectrum generated by MLP and NLP with pulse energy at microjoule level in a zinc telluride capital. The noise-like pulse THz generator will be about 2 to 4 THz wider than that by the mode-locked pulse. Strong THz absorption at 5.3 to 6.9 THz is predicted, as expected from the phonon resonance. The spectrum can be as broad as 50 THz. THz pulse energy generated by NLP is slightly lower than that by the mode-locked pulse generator, at the level of 10-13 Joule level. About an order of magnitude lower.